Open-yard storage of solids in bulk is used for coal, various ores, and similar bulk solids not susceptible to degradation by normal weather condition. As in any type of storage system it is essential to rotate the stored material, that is the first material stored should be the first material reclaimed. This necessitates, of course, reclaiming the material from the bottom of the pile, which in some systems can be several hundred meters long and 10 to 20 meters high.
Accordingly it is a standard practice to form in the ground underneath the normally elongated storage pile an underground tunnel made of reinforced concrete. A heavy-duty conveyor belt is provided in this tunnel. Floor gates, such as described in my earlier patent application Ser. No. 872,832 filed Jan. 27, 1978 allow the material to drop through the floor of the pile, which is also the roof of the tunnel, onto the conveyor belt. It is also known to provide such floor openings with unloading carriages such as described in my copending application Ser. No. 855,270 filed Nov. 28, 1977 (now abandoned).
The disadvantage of such a system is that the construction of the underground tunnel is an extremely expensive operation. Furthermore, in the event that the storage system is no longer needed it is impossible to reclaim the elements of the reclaiming apparatus.